demmt: correctly track object handles used for method 0 on fermi+

Until now, when mapping object to subchannel, object handles were
guessed by using a value passed to method 0.
However, on Fermi+ method 0 accepts object "names", which can differ
from both classes and object handles. Blob uses special ioctl
(IOCTL_CALL/NVRM_MTHD_FIFO_IB_OBJECT_INFO) to get object name from
handle, so we need to parse it and update tracking info.